The overall objectives of this proposal are to characterize the elastic and viscoelastic properties of red cells and to determine how these properties relate to the molecular constituents and utlrastructure of cell membrane. The influence of a number of physiological and pathophysiolgical factors on cell deformability (in a fluid shear field) and ultrastructure (transmission and scanning electron microscopy and freeze etch replicas) will be examined. These will include temperature, pH, cell age, and effects of factors released from platelets, antibodies and uremia. Membrane constituents, e.g., lipids, glycoproteins, spectrin or tektin, will be isolated and characterized by various procedures, including solvent extraction, ultracentrifugation, column chromatography, disc gel electrophoresis and electron microscopy. Denaturation of membrane proteins and phase transitions of lipids will be evaluated by differential scanning calorimetry. We will also investigate the translational mobility of labeled membrane constituents and assess changes in the distribution of labeled membranes associated with changes in cell shape.